Merge Sorted Array

Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

Solution:
If we start from the beginning of array A, it would disturb A's structure.
So we will start from the end of array A after A has expanded it array size.

public class Solution {
    public void merge(int A[], int m, int B[], int n) {
        if (n == 0) return;
        int length = m + n - 1;
        m--;
        n--;
        while(length >= 0){
            if (n < 0) return;
            else if ((m < 0) && (n >= 0)) {
                A[length] = B[n];
                n--;
            } 
            else if(A[m] > B[n]) {
                A[length] = A[m];
                m--;
            }
            else{
                A[length] = B[n];
                n--;
            } 
            length--;
        }
    }
}